The present invention generally relates to semiconductor packaging, and to a method of manufacturing a semiconductor package.
Semiconductor chips include input/output pads that are electrically connected to external circuitry such as terminals in order to function as part of an electronic system. The terminals are typically a lead array such as lead frame. The electrical connections between the chip and the terminals is often achieved by wire bonding, tape automated bonding (TAB) or flip-chip bonding.
Semiconductor packages typically include the chip, the terminals, the electrical connections and an encapsulant. The terminals extend through the encapsulant and are exposed to the external environment for electrical connection to a substrate such as a printed circuit board (PCB), and the encapsulant protects the chip from the external environment to ensure reliability and performance.
Semiconductor packages are often referred to as leaded or leadless packages. In leaded packages, the terminals (or leads) protrude from the encapsulant, whereas in leadless packages, the terminals are aligned with or recessed relative to the encapsulant. For instance, ball grid array (BGA) packages contain an array of solder balls to post on corresponding metal traces on a printed circuit board, and land grid array (LGA) packages contain an array of contact pads that receive corresponding solder traces on a printed circuit board.
Semiconductor packages must constantly reduce size and improve performance and reliability.
In a one approach, a plating mask is provided on a metal carrier. A bump is electroplated on the carrier through an opening in the plating mask until the bump has a mushroom-like shape that includes a cylindrical stem that fills the opening and a hemispherical dome that extends above and laterally beyond the stem and the opening. The plating mask is stripped. A chip is mechanically attached to the carrier using an adhesive. The chip is electrically connected to the bump using a wire bond, An encapsulant is transfer molded on the chip, the bump, the wire bond and the carrier. The carrier is removed from the encapsulant to expose the bump. A contact pad is electrolessly plated on the bump. As a result, the encapsulant extends beneath and anchors the dome, thereby providing a mold lock for the bump.
A drawback to this approach is that the plating mask must be relatively thick in order to form the dome.